GB2271674A

GB2271674A - Cable repair

Info

Publication number: GB2271674A
Application number: GB9221819A
Authority: GB
Inventors: Timothy James Dixon
Original assignee: Northern Telecom Ltd
Current assignee: Nortel Networks Ltd
Priority date: 1992-10-16
Filing date: 1992-10-16
Publication date: 1994-04-20
Anticipated expiration: 2012-10-16
Also published as: DE4332396A1; JPH077828A; GB9221819D0; FR2697111B1; GB2271674B; FR2697111A1

Abstract

A section of straight lay overlapped metal type screen (3) at an intermediate point in a length of cable (1) is replaced by a length of reinstatement screen (8). At each end of the replacement section the original screen is unwrapped from around an underlying dielectric layer (7). The cable is bent into a curve with the unwrapped screen on the inside of the curve. The ends of the reinstatement screen (8) are spliced to the unwrapped ends of the original screen (3). The cable is straightened, and the replacement screen is wrapped and overlapped. <IMAGE>

Description

2271674 CABLE REPAIR

This invention relates to the repair of cables in which a section of overlapped straight-lay metal tape screen surrounding a dielectric layer needs to be replaced with reinstatement screen at some point in the cable intermediate its ends. Such reinstatement may for instance be required in order to remedy a defect occasioned during manufacture of the cable. or in order to make good damage sustained subsequent to manufacture.

In the normal course of manufacture of long lengths of such cable,, the entire length of screen will not be constructed from a single length of metal tape, but will be constructed from a number of lengths spliced end to end. Typically such splicing is achieved by ribbon welding on a new length of tape just before the previous length has been completely deployed. For cable repair, other things being equal, it would generally be found convenient to choose the same method for reinstatement splicing of the metal tape screen as was previously used for splicing the component lengths of screen during intitial manufacture of the cable. This would involve the re-use of a technique already found to be acceptable, whereas the use of a new technique would have to be tested for suitablility. During the initial manufacture of the cable it is relatively easy to splice lengths of metal tape screen by welding immediately prior to the wrapping of the screen around the dielectric layer, but once the screen is in position around the dielectric, welding is generally not practical because it would damage the underlying dielectric.

The present invention is directed to a method of cable repair in which the ends of a length of reinstatement overlapped straight-lay metal tape screen can be spliced in to effect a repair under conditions permitting the splices to be effected out of contact with the underlying dielectric layer.

According to the present invention there is provided a method of cable repair to replace a tape with a length of reinstatement tape that bridges a gap in the original tape separating a first end thereof from a second end, in which method said first and second ends are spaced from around the underlying layer and, while the cable is bent into a curve with the ends on the inside of the curve, the ends of the reinstatement tape are secured to the respective first and second ends of the original tape where those ends are spaced from contact with the underlying layer, whereafter the cable is straightened and the reinstatement tape is closed around the underlying layer.

The invention further provides, in respect of a cable with an overlapped straight-lay metal tape screen wrapped around a dielectric layer, a method of cable repair to replace an intermediate length of the original metal tape screen with a length of reinstatement metal tape screen that bridges a gap in the original screen separating a first end thereof from a second end, in which method said first and second ends are unwrapped from around the dielectric layer and, while the cable is bent into a curve with the unwrapped ends on the inside of the curve,, the ends of the reinstatement length of metal tape screen are secured to the respective first and second unwrapped ends of the original screen where those ends are spaced from contact with the dielectric layer, whereafter the cable is straightened and the reinstatement screen is wrapped in overlapping relationship around the dielectric layer.

There follows a description of a method of cable repair embodying the invention in a preferred form. The description refers to the

TI accompanying drawings in which Figures 1 to 4 depict successive stages in the making of the repair.

Referring to Figure 1, a portion of cable 1, where it is desired to replace a section of damaged, or otherwise unsatisfactory, overlapped straight-lay metal tape screen surrounding a dielectric layer, is held between two cable clamps 2. Between the two clamps a section of outer sheath is removed to expose an underlying metal tape screen 3 (Figure 2). This is a straight lay tape screen with one side edge 4 of the tape overlapping the other side edge 5. The portion of screen that needs to be replaced is removed, leaving two exposed ends 6 (Figure 3) of the original screen. These ends are unwrapped from aroundthe dielectric layer 7, and the cable is bent into a curve, as depicted in Figure 4, with the original screen ends 6 on the inside of the bend. A reinstatement length 8 of metal tape screen is placed with its ends overlapping the original screen ends by an amount leaving a distance Id' between the overlapped portions equal in length to the distance existing between the ends 6 before the cable was bent. This reinstatement length 8 is then secured to the ends 6 for instance by welds 9 extending at an angle across the full width of the tape screens. Because of the bend in the cable, these welds can be performed in regions of the original and reinstatement screens at a sufficient distance from the dielectric layer 7 to enable these welds to be effected without damaging that layer. The cable is then straightened, thereby bringing the reinstatement length of screen into contact with the dielectric layer. The reinstatement length is then wrapped around the dielectric layer and, being the same width as the original screen, it is overlapped in the same manner as the original screen.

At this stage the reinstatement of the screen is complete, and the cable is ready for reinstatement of the cable sheath. A mould (not shown) can for instance be arranged around the cable, and the reinstatement sheathing (not shown) created by extrusion, or alternatively the reinstatement sheathing may be -4constituted by a length of heat-shrink tubing (not shown). When employing heat-shrink tubing, it is preferred to employ tubing that is internally lined with a layer of melt-flowable plastics material. Preferably the shrinkage is commenced near the middle and is caused to progress to both ends wehereby the lining is caused to flow in such a way as to eliminate substantially all voids.

7

Claims

CLAIMS.

1. A method of cable repair to replace a tape with a length of reinstatement tape that bridges a gap in the original tape separating a first end thereof from a second end, in which method said first and second ends are spaced from around the underlying layer and, while the cable is bent into a curve with the ends on the inside of the curve, the ends of the reinstatement tape are secured to the respective first and second ends of the original tape where those ends are spaced from contact with the underlying layer, whereafter the cable is straightened and the reinstatement tape is closed around the underlying layer.

2. In respect of a cable with an overlapped straight-lay metal tape screen wrapped around a dielectric layer, a method of cable repair to replace an intermediate length of the original metal tape screen with a length of reinstatement metal tape screen that bridges a gap in the original screen separating a first end thereof from a second end, in which method said first and second ends are unwrapped from around the dielectric layer and, while the cable is bent into a curve with the unwrapped ends on the inside of the curve, the ends of the reinstatement length of metal tape screen are secured to the respective first and second unwrapped ends of the original screen where those ends are spaced from contact with the dielectric layer, whereafter the cable is straightened and the reinstatement screen is wrapped in overlapping relationship around the dielectric layer.

3. A method of cable repair as claimed in claim 1 or 2, wherein the ends of the reinstatement length of metal tape screen are secured to the respective first and second unwrapped ends of the original screen by welding.

4. A method of cable repair substantially as hereinbefore described with reference to the accompanying drawings.

5. A cable containing at least one repair effected by the method claimed in claim 1, 2, 3 or 4.